This invention relates to article handling systems, and, more particularly, to a method and apparatus for singulating articles and establishing a controlled inter-article gap.
In mail processing, airport baggage claim service, assembly line operations and other applications involving transport and processing of various articles, it is often necessary to separate articles randomly received, sometimes enmass as a slug, stack or pile, into a stream of successive articles. This process of separating articles is generally referred to as xe2x80x9csingulationxe2x80x9d. In a post office or delivery service, for example, packages may arrive at a conveyor system in randomly occurring slugs, the packages in each slug varying significantly in quantity, size and shape within allowed ranges. Singulating such packages or other articles is an essential preliminary step in performing sortation or most other operations on such articles. For the articles to be sorted or otherwise processed, they also must, in most cases, be separated by a gap of sufficient length. However, while at least a minimum gap between succeeding articles is required, spacing larger than the required minimum gap decreases throughput.
Automation apparatus is normally employed for article singulation and establishing proper article separations, such prior art apparatus using belt and chute systems, cameras and/or arrays of photo sensors for each belt to determine positioning of articles on the belts, and mechanisms ranging from robotic arms, to mechanical guides, to complicated control logic for slowing down and speeding up the belts in order to separate the articles to achieve singulation. Gapping apparatus involve various sensors for determining existing leading-edge to leading-edge or trailing-edge to leading-edge distance; gaps are adjusted to desired sizes via mechanical means.
While, combined, a singulation and a gapping apparatus would accomplish the task of singulating and gapping articles, such apparatus has heretofore been expensive and hard to operate, requiring the use of sophisticated technology. There exists a need for an apparatus that is capable of achieving either one or both goals without the use of cameras, computers to analyze digital images, or other expensive equipment.
In accordance with the above, this invention provides a method and an apparatus for singulating articles received in a slug and/or manipulating such articles, particularly articles of various size, to create a controlled gap between the trailing-edge of a leading article and a leading-edge of a successive article. For singulation, a plurality of belts are provided, mounted adjacent to each other, with a slide chute between each pair of adjacent belts, articles being received on a first of the belts and passing from one belt to an adjacent belt through the chute therebetween. A plurality of sensors are positioned such that there is a single control sensor for at least selected ones of the belts, each control sensor sensing article position relative to a corresponding belt. Controls are provided for operating each belt in response to a corresponding control sensor and an operative state of a downstream belt.
The control sensor may be located at an end of a corresponding belt, for example, the exit end of the corresponding belt. The controls may be operative to initiate stopping of a belt if a downstream belt is not running and a corresponding control sensor has been blocked for a configurable period of time. Similarly, the controls are operative to start or re-start a belt when the downstream belt is running. For preferred embodiments, the configurable time period is such that the belt has not completely stopped when a run signal is sent. The configurable time period may also be adjustable to achieve a desired apparatus throughput, such adjustment, for example, being according to an adjustment schedule. The controls may, for example, include at least one subroutine for each belt which is run on an appropriate processor.
The invention also includes apparatus for receiving articles in a stream and creating a controlled gap between a trailing-edge of a leading article and a leading-edge of a successive article. This apparatus includes a plurality of belts mounted adjacent each other, articles being received on a first of the belts and passing from one belt to an adjacent belt. A plurality of control sensors are positioned such that there is a single control sensor sensing article position relative to each belt and controls are provided which operate each belt in response to a corresponding control sensor and an operative state of a downstream belt. The control sensor may be located at an end of a corresponding belt, for example, the exit end of such belt.
The plurality of belts may be logically divided into a first section which minimizes a gap time and a second section which establishes at least a minimum gap time between successive articles. The controls are operative to initiate stopping of a belt in the first section if a downstream belt is not running and a corresponding control sensor is blocked and to send a run signal when the downstream belt is running again. The controls are also operative to initiate stopping of a belt in the second section if a detected trailing-edge to leading-edge gap time is smaller than the desired minimum gap time, and a run signal is sent to the belt after a calculated time period, the calculated time period being a function of a difference between the detected gap time and the minimum gap time. More specifically, calculation of the above function includes: (a) setting the calculated time period to be equal to the difference between the detected gap time and the minimum gap time if the difference is larger than a determined fraction of the minimum gap time; and (b) setting the calculated time period to be equal to a fraction of the minimum gap time if the difference between the detected gap time and the minimum gap time is smaller or equal to a determined fraction of the minimum gap time. The controls are also operative to initiate stopping of a belt, or at least a subset of the plurality of belts, if a corresponding control sensor has been blocked for more than a predetermined time period, which time period may be adjusted to target the desired throughput. For some embodiments, the predetermined time period is smaller than, or at most equal to a time it would take for a longest article to move past the corresponding control sensor. The controls preferably consist of at least one subroutine for each belt.
The invention further includes a method usable with an apparatus for manipulating articles of various size which includes stages of belts carrying the articles and belt controls for stopping and starting the belts, the method maintaining a desired article throughput and including the steps of: (a) monitoring throughput for the article manipulation; and (b) controlling stop time intervals for at least selected ones of the belts to maintain the desired throughput. The step of controlling stop time intervals, step (b) above, may include: (c) adjusting at least selected stop time intervals upward by a selected amount if current throughput is greater than the desired throughput; and (d) adjusting at least selected stop time intervals downward by selected amounts if current throughput is less than the desired throughput. The stop time intervals in steps (c) and (d) above may be adjusted according to at least one adjustment schedule which adjustment schedule is stored in a computer on which control subroutines are run.
The invention further includes apparatus for manipulating articles while maintaining a desired throughput, which apparatus includes stages of belts carrying the articles, and controls operating each belt, the controls being operative to stop and start the belts, and including subroutines for monitoring throughput for the article manipulation and for controlling stop time intervals for at least selected ones of the belts to maintain the desired throughput. The subroutines for controlling stop time intervals may include (a) a subroutine for adjusting at least selected intervals upward by a selected amount if current throughput is larger than the desired throughput; and (b) a subroutine for adjusting at least selected intervals downward by a selected amount if current throughput is smaller than the desired throughput. The adjustments by subroutines (a) and (b) above may be according to an adjustment schedule.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings, the same reference numerals being used for common elements in the various figures.
Finally, the invention includes apparatus for receiving articles in a slug, singulating the articles and creating a controlled gap between a trailing-edge of a leading article and a leading-edge of a successive article. This apparatus includes a plurality of belts mounted adjacent each other, articles being received on a first of the belts and passing from one belt to an adjacent belt. A plurality of control sensors are positioned such that there is a single control sensor sensing article position relative to each belt and controls are provided which operate each belt in response to a corresponding sensor and an operative state of a downstream belt.